The canal aligned on the natural watershed line is called:

Ridge Canal
→ It is also called a watershed canal.
→ Aligned along the ridge or natural watershed line.
→ Can irrigate areas on both sides of the ridge.
→ Cross drainage work is not required.
→ They are economical.

Contour Canal
→ Aligned nearly parallel to the contours of the country.
→ Can irrigate areas only on one side.
→ Cross drainage works are required.

Side Slope Canals
→ Aligned roughly at right angles to the contour of the country.
→ It is neither on the watershed nor in the valley.
→ It can irrigate areas only on one side.
→ It is roughly parallel to the drainage of the country, so cross drainage works are not required.
→ It has a very steep bed slope.